Never mind . . . I just found my answer! It was only after I submitted the question that possible answers came up from a previous discussion (I don't know why it didn't show up when I searched for an answer prior to posting). Nevertheless, for the benefit of anyone else with the problem, I found the answer here:
And the new driver that fixed the issue was posted on that discussion with this link:
Funny that this driver comes from the "UK" (British) version of Samsung's site. It didn't seem to appear on the U.S. version when I tried downloading drivers last week. I guess it's possible that I didn't follow the installation steps in the proper order somehow (even thought I tried it several times.)
But, if you're interested, the successful procedure I used was as follows:
(1) I downloaded the new print driver but did not install it, leaving it on my desktop.
(2) I started the computer in Safe Mode (which might not have been necessary but I did it anyway) then brought up the System Preferences/Printing & Fax Preferences dialogue box, right-clicked on it and chose "Reset Print Queue" making sure there were no printers in the box.
(3) Then I restarted the computer normally and installed the new driver.
(4) I reopened the Printing & Fax Preference Pane and checked to make sure the new driver was the only one in the box. It was.
(5) I opened a plain text document and chose Print. VOILA!—After a slower than usual first start (only a few extra seconds) it printed perfectly and has been working properly ever since.